Interferon is an important antiviral and antitumor protein produced by the human body. Because of its species specificity, clinical use of interferon requires human interferon. Based on their neutralization by antibodies, three types of interferon have been defined which include interferon-alpha, produced mainly by leucocytes, interferon-beta, produced mainly by fibroblasts, and interferon-gamma, produced mainly by T-lymphocytes.
The major species of interferon produced by human fibroblasts in response to ds RNA is the 20 Kd glycoprotein IFN-.beta..sub.1, encoded by a 0.9 kb RNA which is transcribed from an intron-less gene on chromosome 9. However, additional mRNAs which yield IFN activity when microinjected into frog oocytes, have been observed in human fibroblasts induced by poly (rI)(rC) and by a sequential cycloheximide (CHX)-Actinomycin D treatment. While cloning the IFN-.beta..sub.1 cDNA, cDNA clones of another co-induced 1.3 kb RNA have been isolated which in reticulocyte lysates code for a 23-26 Kd polypeptide and in oocytes produce human IFN antiviral activity (J. Weissenbach et al. (1980) Proc. Natl. Acad. Sci. USA 77:7152-7156; British patent 2063882). Since this activity was inhibited by anti-IFN-.beta..sub.1 antibodies, it was designated IFN-.beta..sub.2. The protein product of IFN-.beta..sub.2 RNA is immunologically distinct from IFN-.beta..sub.1, although the biological activities of the two proteins are cross-neutralized by the same antibodies. The IFN-.beta..sub.2 1.3 kb RNA clearly originates from another gene than IFN-.beta..sub.1, since IFN-.beta..sub.2 RNA is formed in mouse-human hybrids lacking chromosome 9 (U. Nir (1984) Ph.D. Thesis, Weizmann Institute of Science, Rehovot, Israel).